The present invention relates to a unit for discharging loose material from a dispensing device.
The unit can be used in particular in the chemical and/or pharmaceutical industry and for any applications where containers of powder, fine-grain pellets or similar products need to be emptied.
The containers are emptied at a discharge station and the material they contain is transferred to a tank connected, for example, to a machine that uses the loose material for subsequent processes.
A supporting structure keeps the tank below the level of the container so that the container is emptied by gravity.
To transfer the material from the container to the tank, connection means, consisting, for example, of a rigid, cylindrical tube with a vertical axis, are used.
These connections must be well sealed so that the powdered material does not escape into the outside environment during its transfer through the tubular bag.
The seal must be especially effective if the powder concerned consists of chemical substances or compounds that are not biodegradable or potentially dangerous.
Moreover, when changing over from one material to another, the tubular bag must be substituted and the connection thoroughly cleaned.
Usually, the top end of the cylindrical tube is equipped with an airtight annular element or spacer designed to securely hold the top end of the tubular bag to the container.
The bottom outfeed end of the container mounts a valve element designed to open and close the bottom end itself.
This valve element usually consists of a butterfly valve equipped with a flat, disc-shaped shutter designed to rotate in both directions about a horizontal axis between a closed position where the shutter closes the bottom end of the container and lies in a substantially horizontal plane, and an open position where the shutter lies in a substantially vertical plane to enable the material to be discharged from the container into the cylindrical tube.
The bottom end of the annular element also has a removable shutoff element (shutter element).
Traditional discharge units of this type are unsatisfactory in that they contaminate the surrounding environment. The main disadvantage is due to the fact that the face of the disc-shaped element that faces the outside when the valve element is closed is turned in the vertical position while the container is being emptied and comes into contact with the powder product being discharged. Product thus sticks to the disc-shaped element and can be released into the surrounding environment when the valve element is closed.
Another disadvantage is that the top end of the spacer, which has also come into contact with the powder product, remains open while the container is being removed.
European patent publication EP 1.043.252 discloses a discharge unit in which the valve element consists not of a single disc-shaped element, as described above, but two disc-shaped shutoff elements that are superposed and releasably connected to each other.
The valve element opens and closes in the same way as the type described above but when the container is changed, the two elements are detached and one of them moves to a position where it closes the outfeed end of the empty container, while the other closes the top end of the spacer, preventing contact between the contaminated parts and the outside environment, facing the faces that were previously in contact with each other.
Although this type of discharge unit is a considerable improvement on traditional discharge units, it too has drawbacks relating to contamination of the environment.
It has been found that, when the two elements are turned to the vertical position and are covered by the product flowing over them during discharge operations, the close contact between the two superposed disc-shaped elements, accomplished by pneumatic or magnetic means does not prevent a significant quantity of powder from finding its way into the outermost portion of the two elements, which is substantially in the shape of a circular crown.
The aim of the present invention is to overcome the above mentioned drawback by providing a unit for discharging loose material from a container, whose components can be cleaned in place without permitting contamination of the outside environment.
In accordance with the invention, this aim is accomplished by a unit for discharging loose material from a dispensing device to a user unit, comprising a tube leading to the user unit, a valve element connecting the dispensing device to the tube infeed end, having an axis extending in a defined direction, the valve element comprising a first annular element, coaxial with the infeed end and comprising shutter means equipped with a first shutoff element and a second shutoff element connected to each other by releasable means and being mobile from a position in which the infeed end of the tube is closed by an airtight seal to a position where it is open, wherein the valve element comprises a second annular element coaxial with the first annular element and forming the infeed end of the tube, the first shutoff element consisting of a disc-shaped element for closing the first annular element, and the second shutoff element consisting of a screen for closing the second annular element, the valve element further comprising sealing means positioned between the first and second annular elements, separation means mobile between a first rest position where the first annular element and the related first shutoff element are respectively in contact with the second annular element and the related second shutoff element and a working position where the first and second annular elements are separated respectively from the related first and second shutoff means in such a way as to form between the shutoff elements a gap that is delimited by the sealing means, and means for cleaning the gap also being provided.
Another aim of the present invention is to provide a method for discharging loose material from a dispensing device to a user unit.
In accordance with the invention, this aim is accomplished by a method for discharging loose material from a dispensing device to a user unit, comprising a tube leading to one end of the user unit itself, a valve element connecting the dispensing device to the tube infeed end, having an axis extending in a defined direction, the valve element comprising a first annular element, coaxial with the infeed end and shutter means equipped with a first shutoff element and a second shutoff element connected to each other by releasable means and being mobile from a position in which the infeed end of the tube is closed by an airtight seal to a position where it is open, the method comprising the steps of: separating the first annular element from a second annular element, which is coaxial with the first annular element and which forms the infeed end of the tube, in such a way as to form a gap between the shutoff elements; isolating the gap through sealing means positioned between the first and second annular elements; and cleaning the gap.